The laboratory continues to search for viruses that can produce diabetes in animal and man. Extensive studies over the last several years have shown that the development of encephalomyocarditis (EMC) virus-induced diabetes depends on the genetic background of the host and the genetic makeup of the virus. Recently, we found that Mengovirus 2T can infect and destroy pancreatic beta cells and produce a diabetes-like syndrome in mice. More detailed studies over the last year have revealed that whereas EMC virus causes diabetes in only certain inbred strains of mice, Mengovirus 2T caused diabetes in strains of mice resistant to EMC virus-induced diabetes. The ability of Mengovirus-2T to induce diabetes in EMC-resistant mice was found to be due to the greater capacity of Mengovirus 2T as compared to EMC virus to replicate in and destroy the islets of these animals. In addition, we found that Cotton rats develop diabetes when infected with a lethal dose of Mengovirus 2T. We also have preliminary evidence that monkeys develop abnormal glucose tolerance tests when infected with certain viruses and subdiabetogenic doses of streptozotocin.